I won't even know what to offer, no idea how much they are worth currently... I'll check, but please answer following questions:
1. Does this PSU power all units without a problem? Are all required cables included?
The psu was being used to power the 3 ones that are fanless, and the cables to do so are provided.
It should be able to power all 5, although i didn't make cables for the other 2 as they were used in a different location.
2. How much would be shipping to Poland?
According to seur.com it would be 41,79€ of shipping. Perhaps some other delivery service will be cheaper, but is the only one i know.
I think a fair price would be 25€ per gridseed.